A vehicle control system that automatically unlocks doors when a user approaches a vehicle and automatically locks the doors when the user walks away from the vehicle has been put into practical use. The system includes a vehicle control apparatus mounted on the vehicle; and a portable device carried by the user.
The vehicle control apparatus transmits a response request signal in a predetermined cycle, and the user's portable device receives the response request signal. When the user approaches the vehicle and the portable device receives a response request signal of a certain level or higher, the portable device sends a response signal including an ID code back to the vehicle control apparatus. When the vehicle control apparatus receives the response signal, the vehicle control apparatus authenticates the ID code. If the authentication result is normal, then the vehicle control apparatus performs control to, for example, unlock the vehicle doors and turn on lighting that illuminates an area around the user's feet near the doors. A function of, for example, thus automatically unlocking the doors and automatically turning on the lighting when the user approaches the vehicle is called “welcome entry”, and referred to as “WE” in the following.
On the other hand, when the user gets out and walks away from the vehicle and the strength of the response request signal received by the portable device is reduced to a predetermined value, the portable device stops the sending back of the response signal. When the vehicle control apparatus determines that the response signal from the portable device has been stopped, the vehicle control apparatus locks the vehicle doors. A function of thus automatically locking the doors when the user walks away from the vehicle is called “walk away lock”, and referred to as “WAL” in the following.
JP 2001-90402 A describes a vehicle control system including the WE and WAL functions such as those described above. In this system, when a user carrying a portable device walks away from a vehicle, doors are locked at a point in time when the user has walked away to a position within a relatively short distance from the vehicle (WAL), and when the user approaches the vehicle, the doors are unlocked at a point in time when the user has approached a position within a relatively long distance from the vehicle (WE). By this, the user having got out of the vehicle can easily check the locking of the doors near the vehicle, and for the user rushing to the vehicle, the doors can be unlocked in good time.
However, in the conventional vehicle control system, a distance between the portable device and the vehicle at a point in time when the doors are unlocked in WE and a distance between the portable device and the vehicle at a point in time when the doors are locked in WAL are both fixed values which are preset as threshold values. Therefore, the user cannot freely change the distances.